Margulies will guest-star in two episodes slated for November broadcasts.

Cavanagh reprises his role as J.D.'s older brother and pays a visit when their father unexpectedly passes away. He will appear in two episodes, which will air in October.

"When I heard that Julianna was a fan of 'Scrubs,' I jumped at the chance to get her on-board for a couple of episodes," said Bill Lawrence, the series' creator. "Her character is going to be a giant thorn in everyone's side and will really shake things up with a malpractice suit at the hospital." Lawrence further adds, "Tom and Zach have this amazing rapport with each other and that adds a certain realness to the show. I was thrilled that he agreed to return to this role."

Margulies starred for six seasons on NBC's long-running drama series "ER," for which she won an Emmy Award for outstanding supporting actress in a drama series. Most recently, Margulies wrapped "Slingshot" opposite David Arquette and Balthazar Getty, and was last seen in the mini-series "The Grid" alongside Dylan McDermott. Her feature-film credits include "Ghost Ship," "Evelyn" and "The Newton Boys."

Cavanagh's breakthrough performance as Ed Stevens on "Ed" earned him a Golden Globe nomination and the TV Guide Award for Favorite Actor in a New Series. He recently wrapped production on the upcoming TV movie "Snow," where he stars as "Nick Snowden", the son of Santa Claus. Prior to that, he starred in two independent feature films "Alchemy," with "Scrubs'" star Sarah Chalke and "Flood of Fear." His additional television credits include a recurring role on "Providence" and the TV movies "Anya's Bell" and "Bang, Bang, You're Dead." His feature credits include the family drama "Northern Lights," as well as the adventure "Magic in the Water" and the action-thriller "Mask of Death." Cavanagh's additional film credits include "The Dukes," "Honeymoon," "Movin' On Up" and "Car 54."

Winner of a prestigious Humanitas Prize and a People's Choice Award, and nominated for a Producer's Guild and five Emmy Awards, "Scrubs" focuses on the strange experiences of fresh-faced medical resident John "J.D." Dorian (Zach Braff) as he embarks on his healing career in a surreal hospital crammed full of unpredictable staffers and patients ? where humor and tragedy can merge paths at any time.

Keeping a watchful eye over these young doctors are the caustic chief of medicine, Dr. Bob Kelso (Ken Jenkins), the abrasive but caring Dr. Perry Cox (John C. McGinley), and Neil Flynn as the hospital janitor ? and J.D.'s nemesis.

"Scrubs" is produced by Touchstone Television. Bill Lawrence ("Spin City") is the executive producer and creator.